BIOCHEMICAL AND PHYSICAL CHARACTERIZATION OF HARD WINTER WHEAT QUALITY FOR END-USE QUALITY
Location: Grain Quality and Structure Research Unit
Title: Protein and quality characterization of complete and partial near isogenic lines of waxy wheat
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2010
Publication Date: December 1, 2010
Citation: Jonnala, R.S., Macritchie, F., Smail, V.W., Seabourn, B.W., Tilley, M., Lafiandra, D., Urbano, M. 2010. Protein and quality characterization of complete and partial near isogenic lines of waxy wheat. Cereal Chemistry. 87(6):538-545.
Interpretive Summary: Waxy wheats have found application in the production of modified starches, as blends in flour for superior noodle quality, and in enhanced bread making performance. Starch based properties such as pasting and gelatinization differ between waxy, partial waxy and non-waxy wheats. However, except for starch properties, there is limited information about the quality characteristics of partial waxy and complete waxy wheats. There is an obvious need to study waxy wheat protein composition and its effects on dough and end-use product quality. In this study, the effect of waxy and partial (single and double null) waxy proteins on flour quality and physical dough testing parameters using two sets of near isogenic lines developed in a durum wheat cultivar (Svevo) and a bread wheat line was evaluated. Results showed that loaf volume, which is an important bread making quality, was highest with 100% waxy wheat flour and was not improved with 50% blending with commercial bread wheat flour. However, dark color and poor appearance with large gas cells in the internal crumb were observed with 100% waxy flour; this is unacceptable to consumers of traditional pan bread. In terms of protein composition, waxy wheats have relatively lower albumins/globulins than regular wheat. Dough strength parameters such as MDDT and Rmax were poorly correlated with UPP whereas loaf volume and extensibility were highly and positively correlated with FPP and PPP.
The objective of this study was to evaluate protein composition and its effects on flour quality and physical dough test parameters using waxy wheat near-isogenic lines. Partial waxy (single and double nulls) and waxy (null at all three waxy loci, Wx-A1, Wx-B1, and Wx-D1) lines of N11 set (bread wheat) and Svevo (durum) were investigated. For protein composition, waxy wheats in this study had relatively lower albumins-globulins than the hard winter wheat control. In the bread wheats (N11), dough strength as measured by mixograph peak dough development time (MDDT) (r = 0.75) and maximum resistance (Rmax) (r = 0.70) was significantly correlated with unextractable polymeric protein (UPP), whereas in durum wheats, moderate correlation was observed (r = 0.73 and 0.59, respectively). This may be due to the presence of high molecular weight glutenin subunits (HMW-GS) Dx2+Dy12 at the Glu-D1 locus instead of Dx5+Dy10, which are associated with dough strength. Significant correlation of initial loaf volume (ILV) to flour polymeric protein (FPP) (r = 0.75) and flour protein (FP) (r = 0.63) was found in bread wheats, whereas in durum wheats, a weak correlation of ILV was observed with FP (r = 0.09) and FPP (r =0.51). Significant correlation of ILV with FPP in bread wheats and with % polymeric protein (PPP) (r = 0.75) in durum lines indicates that this aspect of end-use functionality is influenced by FPP and PPP, respectively, in these waxy wheat lines. High ILV was observed with 100% waxy wheat flour alone and was not affected by 50% blending with bread wheat flour. However, dark color and poor crumb structure was observed with 100% waxy flour, which was unacceptable to consumers. As the amylopectin content of the starch increases, loaf expansion increases but the crumb structure becomes increasingly unstable and collapses.